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Interesting, mine's been doing

that for several years now. Thought it was my secondary air pump grinding on cold-weather starts so replaced it along with the valve but still making that noise. Just as described by dc52241, seems something isn't disengaging immediately after startup.

Now wondering if I should make it right or let it slide!
Thanks! something else to look into :)

Starter solenoid

As described briefly above by edjack, the starter solenoid (slightly different from a Bendix drive, according to Wikipedia) throws the starter pinion into engagement with the ring gear when you turn the key into the start position. When you release the key, a spring in the solenoid unit is supposed to force the pinion gear out of engagement with the ring gear. One of the failure modes is for the pinion shaft to get "sticky" so that the spring retraction is slow and the ring gear teeth will munch on the pinion a bit until it gets out of the way. In old days, you could rebuild or replace just the starter solenoid on an otherwise perfectly good starter motor. Nowadays, of course, you install a complete rebuild starter motor assembly and turn in your defective one (the "core"). Preferably, get a Bosch rebuilt starter motor instead of a Magnetti Marelli.
'97 528i Montreal Blu./Grey
'98 323is Arctic Sil./Blk, SP
'95 M3 Cosmos Blk./Blk

Where to buy rebuilt???

Re: Starter grind/squeal after starting Help

I also have this noise on starting, but only on rare occasions. I have been trying to track it down for about a year but it will never do it when I have the hood open and listening.

I went to my service department a few months ago in hopes that it would occur while there - but no such luck.
HOWEVER - the service manager and technician both said that it is "most likely" the starter, and the fault is as described in the other messages below - the starter not withdrawing quickly.

They made the point that if it continues then, in their experience, it can go beyond needing a new starter. If the teeth on the flywheel begin to be damaged then it is necessary to pull the engine and replace the flywheel as well - and that is $$$.

The teeth on the flywheel are also used by the engine computer. The crankcase position sensor reads the passing of the teeth and uses that information for many aspects of timing and misfire analysis. It is precise enough that the computer has a diagnostic routine to measure the "exact" position of each tooth while the engine is coasting so that it can account for slight differences in spacing between the teeth due to slight differences in manufacturing tolerances. So obviously any wear of the teeth will also affect this process.

I will probably be replacing my starter soon, just as soon as I can figure out if my alternator is also starting to go (noisy).

Early CPS problems

Those missing ring gear teeth were devilish when crankshaft position sensors first came out. I recall a 750i at my friend's BMW dealership about 15-20 years ago that would start perfectly every time, then promptly start misfiring worse and worse until it would stall. They went nuts trying to diagnose it until they found a chipped tooth on the ring gear. The owner admitted that he had mistakenly tried to start the engine while it was running, the V12's idle so smoothly. It was one of the first models/years that the ignition timing was related to the CPS.
'97 528i Montreal Blu./Grey
'98 323is Arctic Sil./Blk, SP
'95 M3 Cosmos Blk./Blk

Relay or ignition JimLev?

Read a post Jimlev had about this possibly being the relay or ingnition circut failing. Possible that it is staying on causing the starter to stay engaged? Did anyone else read this or diagnose this way.

Is the grinding noise as soon as U turn the key (m

to the start position? If so, the starter drive teeth are not meshing with the flywheel teeth properly. Could be like edjack says or you could have a chipped tooth and it's rotational position only is at the starter location every once in a great while.
If the starter is staying engaged after the engine starts, this could also be a bad starter, or possibly the atarter relay (behind the glove box) isn't releasing when you release the key. Might be ignition switch too.
I'd pull the starter and look at the shaft that the pinion gear slides on. Clean and lube it with a light coat of grease. Also look at all the teeth on the flywheel as you have someone turn the engine over with a big wrench on the crankshaft pulley. Take the spark plugs out, it will turn over much easier.

Only for split second after it starts up

It only makes the squeal/grind for a second after startup. i orderd a new ignition switch. Figure worse case it is not the ignition and I will ebay old one. Seems to do this when I crank key all the way forward, if I am gentle with it. Does not seem to do so. Basically if I turn the key to the back of the crank position it will make the noise once every 4-6 starts. Been gentle just to front of crank position and does not seem to do this.

From what you say it could be the contacts in the(

ignition switch. When you take out the old switch open it up and see what the contacts look like. IIRC the 2 halfs of the switch unsnap. Look for signs of arc/burnt mark on the contacts.
I bought a new one last year just in case, it's been in my trunk along with the cam and crank position sensors.....so now I'll probably never need them!

Re: Interesting, mine's been doing

Same here 97 528/5 always thought it's the sec air pump.On the other hand it only does it in cold weather,on a cold engine only,never on a warm engine,wouldn't starter/solenoid etc problems be independent of engine or ambient temps?

That's what I'm thinking...(long)

For example today when I first cold started in the morning, I heard the split-second grind after motor starts, but with a startup a few hours later it was normal without the noise.

I too thought it was the sec air pump and so replaced it, only to hear the noise again. I replaced the sec air pump because 1 - it was 10 years old, and 2 - I gathered from previous posts here that the sec air pump performs its function when outside temps are below 50 degrees.

Now I'm guessing that the noise is from the pinion shaft (as JKRIT wrote: "pinion shaft to get "sticky" so that the spring retraction is slow and the ring gear teeth will munch on the pinion a bit until it gets out of the way"). It occurs mostly on cold starts when pinion shaft lubricant would be thicker/sticky, unlike on warm/hot starts when it retracts effortlessly.

Yea so the started selenoid normal operation shouldn't have anything to do with ambient temps except for the "sticky" part, just happened to coincide with sec air pump as possible culprit, diagnosed wrong but am glad I put a new one in anyway.

Can definitely be cold weather dependant

My starter solenoid just started to hang up a bit in late Spring (2005?), then it stopped doing it all Summer. Sure enough, when air temps started dropping in theFall, it started hanging up again, so I replaced the starter.
'97 528i Montreal Blu./Grey
'98 323is Arctic Sil./Blk, SP
'95 M3 Cosmos Blk./Blk